direction.  The 3 lattice directions you specify must be mutually

orthogonal and obey the right-hand rule, i.e. (X cross Y) points in

the Z direction.  Note that this description is really only valid for

orthogonal lattices.  if you are using the more general lattice style

orthogonal lattices.  If you are using the more general lattice style

<I>custom</I> with non-orthogonal a1,a2,a3 vectors, then think of the 3

<I>orient</I> options as creating a 3x3 rotation matrix which is applied to

a1,a2,a3 to rotate the original unit cell to a new orientation in the

<P>If the <I>spacing</I> option is not specified, the lattice spacings are

computed by LAMMPS in the following way.  A unit cell of the lattice

is mapped into the simulation box (scaled, shifted, rotated), so that

it now has (perhaps) a modified shape and orientation.  The lattice

it now has (perhaps) a modified size and orientation.  The lattice

spacing in X is defined as the difference between the min/max extent

of the x coordinates of the 8 corner points of the modified unit cell.

Similarly, the Y and Z lattice spacings are defined as the difference

<PRE>lattice none 

</PRE>

<P>For other lattice styles, the option defaults are origin = 0.0 0.0

0.0, orient = x 1 0 0, orient = y 0 1 0, orient = z 0 0 1, a1 = 1.0

0.0 0.0, a2 = 0.0 1.0 0.0, and a3 = 0.0 0.0 1.0.

0.0, orient = x 1 0 0, orient = y 0 1 0, orient = z 0 0 1, a1 = 1 0 0,

a2 = 0 1 0, and a3 = 0 0 1.

</P>

</HTML>

direction.  The 3 lattice directions you specify must be mutually

orthogonal and obey the right-hand rule, i.e. (X cross Y) points in

the Z direction.  Note that this description is really only valid for

orthogonal lattices.  if you are using the more general lattice style

orthogonal lattices.  If you are using the more general lattice style

{custom} with non-orthogonal a1,a2,a3 vectors, then think of the 3

{orient} options as creating a 3x3 rotation matrix which is applied to

a1,a2,a3 to rotate the original unit cell to a new orientation in the

If the {spacing} option is not specified, the lattice spacings are

computed by LAMMPS in the following way.  A unit cell of the lattice

is mapped into the simulation box (scaled, shifted, rotated), so that

it now has (perhaps) a modified shape and orientation.  The lattice

it now has (perhaps) a modified size and orientation.  The lattice

spacing in X is defined as the difference between the min/max extent

of the x coordinates of the 8 corner points of the modified unit cell.

Similarly, the Y and Z lattice spacings are defined as the difference

lattice none :pre

For other lattice styles, the option defaults are origin = 0.0 0.0

0.0, orient = x 1 0 0, orient = y 0 1 0, orient = z 0 0 1, a1 = 1.0

0.0 0.0, a2 = 0.0 1.0 0.0, and a3 = 0.0 0.0 1.0.

0.0, orient = x 1 0 0, orient = y 0 1 0, orient = z 0 0 1, a1 = 1 0 0,

a2 = 0 1 0, and a3 = 0 0 1.

</PRE>

<UL><LI>one or more keyword/value pairs may be listed 

<PRE>keyword = <I>linestyle</I> or <I>dmin</I> or <I>dmax</I> or <I>lineiter</I>

  <I>linestyle</I> value = <I>secant</I> or <I>scan</I>

  <I>dmin</I> value = min

    min = minimum distance for line search to move (distance units)

keyword = <I>dmax</I>

  <I>dmax</I> value = max

    max = maximum distance for line search to move (distance units)

  <I>lineiter</I> value = N

    N = max number of iterations in a line search 

</PRE>

</UL>

<P><B>Examples:</B>

</P>

<PRE>min_modify linestyle scan dmin 0.001 dmax 0.2

min_modify lineiter 5 

<PRE>min_modify dmax 0.2 

</PRE>

<P><B>Description:</B>

</P>

<P>This command sets parameters that affect the minimization algorithms.

The various settings may effect the convergence rate and overall

number of force evaluations required by a minimization, so users can

experiment with these parameters to tune their minimizations.

</P>

<P>The <I>linestyle</I> sets the algorithm used for 1d line searches at each

outer iteration of the minimizer.  The <I>secant</I> style uses two

successive force/energy evaluations to create a parabola and pick its

minimum as an estimate of the next iteration's 1d minimum.  The <I>scan</I>

style starts its 1d search at <I>dmin</I> and doubles the distance along

the line at which the energy is computed until the minimum is passed.

It continues only as far as <I>dmax</I>.  Normally, the <I>secant</I> method

should find more accurate 1d minimums in less iterations, but the

<I>scan</I> method can be more robust.

</P>

<P>The <I>dmin</I> and <I>dmax</I> settings are both used by the <I>scan</I> line search

as described above.  For the <I>secant</I> line search, only the <I>dmin</I>

value is used to pick an initial point to begin the secant

approximation.

</P>

<P>The <I>lineiter</I> setting is used by the <I>secant</I> algorithm to limit its

iterations.  The smaller the setting, the more inaccurate the line

search becomes.  Nonlinear conjugate gradient is not thought to

require high-accuracy line searches in order to converge efficiently.

<P>This command sets parameters that affect the energy minimization

algorithms.  The various settings may effect the convergence rate and

overall number of force evaluations required by a minimization, so

users can experiment with these parameters to tune their

minimizations.

</P>

<P>The minimization algorithms have an outer iteration (conjugate

gradient or steepest descent) and an inner iteration which is steps

along a one-dimensional line search in a particular search direction.

The <I>dmax</I> parameter is how far any atom can move in a single line

search in any dimension (x, y, or z).  Thus a value of 0.1 in real

distance units means no atom will move further than 0.1 Angstroms in a

single outer iteration.  This is typically set to avoid the

possibility than one atom will be moved through another due to strong

overlapping forces.

</P>

<P><B>Restrictions:</B> none

</P>

</P>

<P><B>Default:</B>

</P>

<P>The option defaults are linestyle = secant, dmin = 1.0e-5, dmax = 0.1,

and lineiter = 10.

<P>The option defaults are dmax = 0.1.

</P>

</HTML>

min_modify keyword values ... :pre

one or more keyword/value pairs may be listed :ulb,l

keyword = {linestyle} or {dmin} or {dmax} or {lineiter}

  {linestyle} value = {secant} or {scan}

  {dmin} value = min

    min = minimum distance for line search to move (distance units)

keyword = {dmax}

  {dmax} value = max

    max = maximum distance for line search to move (distance units)

  {lineiter} value = N

    N = max number of iterations in a line search :pre

:ule

[Examples:]

min_modify linestyle scan dmin 0.001 dmax 0.2

min_modify lineiter 5 :pre

min_modify dmax 0.2 :pre

[Description:]

This command sets parameters that affect the minimization algorithms.

The various settings may effect the convergence rate and overall

number of force evaluations required by a minimization, so users can

experiment with these parameters to tune their minimizations.

The {linestyle} sets the algorithm used for 1d line searches at each

outer iteration of the minimizer.  The {secant} style uses two

successive force/energy evaluations to create a parabola and pick its

minimum as an estimate of the next iteration's 1d minimum.  The {scan}

style starts its 1d search at {dmin} and doubles the distance along

the line at which the energy is computed until the minimum is passed.

It continues only as far as {dmax}.  Normally, the {secant} method

should find more accurate 1d minimums in less iterations, but the

{scan} method can be more robust.

The {dmin} and {dmax} settings are both used by the {scan} line search

as described above.  For the {secant} line search, only the {dmin}

value is used to pick an initial point to begin the secant

approximation.

The {lineiter} setting is used by the {secant} algorithm to limit its

iterations.  The smaller the setting, the more inaccurate the line

search becomes.  Nonlinear conjugate gradient is not thought to

require high-accuracy line searches in order to converge efficiently.

This command sets parameters that affect the energy minimization

algorithms.  The various settings may effect the convergence rate and

overall number of force evaluations required by a minimization, so

users can experiment with these parameters to tune their

minimizations.

The minimization algorithms have an outer iteration (conjugate

gradient or steepest descent) and an inner iteration which is steps

along a one-dimensional line search in a particular search direction.

The {dmax} parameter is how far any atom can move in a single line

search in any dimension (x, y, or z).  Thus a value of 0.1 in real

distance units means no atom will move further than 0.1 Angstroms in a

single outer iteration.  This is typically set to avoid the

possibility than one atom will be moved through another due to strong

overlapping forces.

[Restrictions:] none

[Default:]

The option defaults are linestyle = secant, dmin = 1.0e-5, dmax = 0.1,

and lineiter = 10.

The option defaults are dmax = 0.1.

</P>

<PRE>min_style style 

</PRE>

<UL><LI>style = <I>cg</I> or <I>cg/fr</I> or <I>sd</I> 

<UL><LI>style = <I>cg</I> or <I>sd</I> 

</UL>

<P><B>Examples:</B>

</P>

<P>Choose a minimization algorithm to use when a <A HREF = "minimize.html">minimize</A>

command is performed.

</P>

<P>Style <I>cg</I> is the Polak-Ribiere (PR) version of the conjugate gradient

(CG) algorithm.  At each iteration the force gradient is combined with

the previous iteration information to compute a new search direction

perpendicular (conjugate) to previous search directions.  The PR

<P>Style <I>cg</I> is the Polak-Ribiere version of the conjugate gradient (CG)

algorithm.  At each iteration the force gradient is combined with the

previous iteration information to compute a new search direction

perpendicular (conjugate) to the previous search direction.  The PR

variant affects how the direction is chosen and how the CG method is

restarted when it ceases to make progress.  The PR variant is thought

to be the most effective CG choice.

</P>

<P>Style <I>cg/fr</I> is the Fletcher-Reeves version of the conjugate gradient

algorithm.

</P>

<P>Style <I>sd</I> is a steepest descent algorithm.  At each iteration, the

downhill direction corresponding to the force vector (negative

gradient of energy) is searched along by a 1d line search.  Typically,

steepest descent will not converge as quickly as CG, but may be more

robust in some situations.

search direction is set to the downhill direction corresponding to the

force vector (negative gradient of energy).  Typically, steepest

descent will not converge as quickly as CG, but may be more robust in

some situations.

</P>

<P><B>Restrictions:</B> none

</P>